1. Field of the Invention
The present invention relates to an air conditioning system for an electric car which is provided with an evaporator and a sub condenser within the air conditioning duct and which controls the temperature by adjusting the quantity of air passing through the sub condenser with a mixing door.
2. Description of the Related Art
To cite an example of an air conditioning system in the prior art, the air conditioning system disclosed in Japanese Unexamined Patent Publication S61-101020 is provided with a main coolant circuit that passes through the coolant compressor, the main condenser and the expansion valve to reach the evaporator, and a sub coolant circuit that branches between the coolant compressor and the main condenser via a directional control valve. The sub coolant circuit communicates with the evaporator via the condenser for heating (sub condenser) which is placed in the air passage of the evaporator on the cabin side.
This air conditioning system has a main coolant circuit, which is used for cooling, and a sub coolant circuit, which is used for heating. Switching between cooling and heating is executed by selecting the main coolant circuit or the sub coolant circuit with the directional control valve.
However, in an air conditioning system such as the one described above, since the main coolant circuit, which uses the main condenser, is selected for the cooling operation and the sub coolant circuit, which does not use the main condenser, is selected for the heating operation, and since there is a great difference in the volumetric capacity of the elements which compose the cooling operation cycle and the heating operation cycle, there is a great difference in the correct coolant filling quantity for the two different operations.
Also, depending upon the stopped state of the cycle and the temperature difference, approximately 60% of the coolant filling quantity may remain in the main condenser (a large hold-up volume) and if a heating operation is performed under these circumstances (insufficient gas), such problems as poor heating performance, stoppage of the operation due to a protective device functioning or seizure of components may occur.
Furthermore, if the quantity of the coolant retained in the main condenser is small (a small hold-up volume), there may be too much coolant flowing in the heating cycle and such problems as abnormally high pressure or stoppage due to the functioning of a protective device may occur.